I'm just gonna post this here since I had it saved from 2ch and there is ... still no other info out to confirm or deny if what they posted was real and no scans from Volume 3's BD booklet where it's apparently in? But we got a lot of info from the exhibits and stuff too, so.

But it says:

"I also received BD Volume 3.
The booklet revealed the specifications of Dio's machine.
750.1 km/h maximum speed and 450 km/h cruising speed.
By the way, here are the specs for Fam.
160 km/h cruising speed and 300 km/h maximum speed.
The Vespa would be slower than the Silvius in the Grand Race."

Seriously if that's legit then Dio. Dio.